Best seller. Bobbie Ann Mason's first novel

In Country, by Bobbie Ann Mason. New York: Harper & Row. 245 pp. $15.95. It seems as ironic as war itself that a woman has written one of the best novels yet about Vietnam -- setting most of her story in a tiny town in western Kentucky, more than a decade later.

It is the summer of 1984. Seventeen-year-old Samantha (Sam) Hughes, fresh out of high school, should be plotting her future, deciding between the University of Kentucky and Murray State University. Instead, she is haunted by the past, driven by an obsessive desire to learn more about a father she never knew and a war she cannot understand.

Her search is far from easy. Sam's mother, now living in Lexington, Ky., with a new husband and baby, admits that she can hardly remember Sam's father, her bridegroom of only a month when he was sent to Vietnam, never to return. Emmett, the uncle with whom Sam lives, dismisses her questions about his experiences in Vietnam by telling her, ``Oh, you don't want to know.'' Even Emmett's buddies, veterans all, try to shield her from their collective burden.

``Stop thinking about Vietnam, Sambo,'' one of them tells her. ``You don't know how it was, and you never will. There is no way you can ever understand. So just forget it.''

But Sam can't -- and won't -- forget. ``I feel like there's a big conspiracy against me,'' she says. But she presses on, asking questions no one wants to hear, searching for answers no one will give. Sam is unsophisticated, at times unrefined, and of questionable morality. But she is also wise beyond her years. And as Bobbie Ann Mason unfolds the story of Sam's quest in this beautifully crafted first novel, she draws readers into a gently relentless story about Vietnam and its aftereffects on the Ameri can psyche.

Sam longs to get out of Hopewell, a sadly misnamed town, where, as Emmett says, ``everything's always ten years behind.'' She dreams of going off with her friend Dawn to ``do something real wild,'' like ``get jobs in Florida or somewhere, and go to the beach every day.''

But she is devoted to Emmett, who got ``messed up'' in Vietnam and whose life now revolves around ``M*A*S*H'' reruns, bird watching, breakfast at McDonald's with fellow veterans, and his beloved cat, Moon Pie. She is also fearful that his physical ailments signal exposure to the chemical defoliant Agent Orange used in Vietnam. For his sake Sam scales down her dreams, concluding, ``I'd be satisfied if we could just go to the mall in Paducah.''

In this backwater place, half a world away from Vietnam, everything from Emmett's endless games of Pac Man to the flea bomb he sets off in their house becomes in Sam's mind a metaphor for killing and war. She watches Geraldine Ferraro campaigning on television and thinks, ``She wouldn't get us in a war.'' She notices ``a pool of orange light from a mercury lamp'' in a parking lot and sees the color of napalm. Tropical plants in a suburban mall become jungle plants in Southeast Asia. Even the dark corner s of a dance hall, out of reach of a strobe light, remind her of ``a foxhole where an infantryman would be crouched for the night.''

She tries to imagine the terrain of Vietnam -- jungles and foxholes and rice paddies. (``Did rice grow in rows? Was it bushy, like soybeans? No, it was like grass. It was like wheat growing in water.'') She tries also to simulate the terror that ``the soldiers had felt every minute. They lived with the possibility of unseen eyes of snipers.''

As Sam hacks a path through her own jungle of questions and emotions, as she confronts the snipers lurking in the shadows of her mind, she achieves a measure of understanding, if not peace. And as she extracts from Emmett and his buddies the terrible secrets they have carried within themselves ever since their year ``in country'' -- in Vietnam -- she leaves a reader with hope that this sharing will mark the beginning of healing.

Mason's spare prose, so perfectly suited to her unpretentious characters and setting, gives the book a simplicity that is both deceptive and disarming. She displays an ear perfectly tuned to dialogue, an eye that catches every telling detail and quirky mannerism. Tiny, seemingly insignificant observations and revel ations accumulate almost unnoticed until something trips them, turning them into literary grenades explosive with meaning.

Characters who in less-skilled hands could seem freakish become charming as Mason exposes their foibles with compassion, gentle humor -- even love. One of the best portraits is Mamaw, Sam's paternal grandmother, a large, simple woman as baffled by credit cards as she is by ``little tubs of non-dairy creamer'' in a restaurant. The people are better than their out-of-joint times.

Ultimately, Mason seems to be saying that nobody comprehends war -- any war, especially this war. In filtering a sad chapter in American history through the eyes and mind of a backwater teen-age girl, she offers insights that bring new perspective to years of confusing news reports and TV documentaries.

Not every reader will share Mason's sentiments about Vietnam. But only the most uncaring will be able to ignore the moral questions that lie at the heart of this little volume -- questions an anguished Sam poses quietly and powerfully:

``What would make people want to kill? . . . Why was there war?''